almost overheating

3/4 is about the upper end of normal operating temp on the old gages. If it's not going above that, I wouldn't worry. Just keep an eye on it. Might want to check your timing, too. If it's advanced too much, it will cause it to run warmer. And whatever the stock fan is that you are swapping for a flex fan is probably better than the flex fan, you might want to cancel that order. I run a flex fan in my Duster only because there isn't enough clearance between the pump and radiator to run a vicious clutch fan.